1. Field of the Invention
The present invention relates to a printed circuit transferring apparatus of a surface mounter, and more particularly to a printed circuit transferring apparatus of a surface mounter, enabling to accurately control the positions where the electronic components are to be mounted on a printed circuit board, to make it possible the work at arbitrary positions, and to further provide an easy compensation for any errors possibly occurring in mounting the electronic components.
Further, the present invention relates to a printed circuit transferring apparatus of a surface mounter for mounting various chips as well as surface mounting components on the printed circuit board.
2. Description of the Conventional Art
In developing recent electronic products, there are trends toward their higher density, smaller size and a variety of electronic components, which developments are becoming highly competitive.
In particular, a surface mounting technology is applied to a printed circuit board (PCB) used for mounting the electric and electronic components thereon by a surface mounting apparatus. The use of such a technology is becoming popular.
A surface mounting assembly equipment typically has the surface mounting apparatus as a core apparatus for mounting the surface mounting components on the PCB. The surface mounting apparatus receives the various types of surface mounting components from a part feeder, transfers the components to the component mounting positions, and then performs the mounting of the components on the PCB.
The surface mounting apparatus is greatly classified into two types of apparatuses, i.e., high speed apparatus and general purpose apparatus, depending upon the function thereof. The former one is designed to assemble a great deal of components in a relatively short time period thus resulting in advantageously provision of faster components mounting operation suitable for mass production. However, this type of apparatus has a drawback in the reduced mounting precision. The latter one is adapted to mount various types of components thus resulting in the provision of higher mounting precision and the feasibility of the mounting of various components. The general purpose apparatus has an advantage for smaller amount of production of various components, but the drawback is its lower throughput caused by the production in retard.
The surface mounting apparatus consists of a feeder (hereinafter, referred to as xe2x80x98tape feederxe2x80x99) for supplying components, X-Y gantry for determining the mounting positions, a conveyer for carrying a PCB, a header unit for orderly picking up the components from the tape feeder and mounting the same onto the PCB.
The surface mounting apparatus generally refers to an apparatus adapted to mount electronic components, including various chips, on a PCB, and is also collectively called as a mounter.
The detailed structure of the above mentioned mounter will be described below.
The conventional mounter consists of: a base assembly; a conveyer unit disposed on an upper portion of the base assemble, and for carrying the PCB; a feeder unit for supplying various chips or surface mounting components so that these components can be mounted on the PCB; a mounter head assembly for mounting respective components suppled from the feeder unit on the PCB; a sensing unit for sensing the components and correcting the positions thereof such that various components to be mounted by the mounted head assembly can be accurately mounted; an X-Y gantry unit provided with the sensing unit and the mounter head assembly, and for positioning same using an X-Y table; and the others.
The X-Y gantry unit is structured such that one block is moved to a position designated by a X-Y table to perform the mounting work. Herein, said one block consists of plural general-purpose heads and precision specific-purpose heads and functions in such a manner that the electronic components are centered.
The centering performance for respective electronic components greatly depends on whether what type of feeders is used to supply the components or what type of cameras is employed.
The above-mentioned sensing units are, respectively, disposed on front and rear sites, in consideration of the work efficiency. One sensing unit located in the front site is for sensing the components fed from the feeder positioned at a front feeder base, while the other sensing unit located in the rear site is for sensing the components fed from another feeder positioned at a rear feeder base. These sensing units acquire images of the components to use same at the time mounting the electronic components.
The conveyer unit carries the PCB on which various chips are to be mounted, and functions to transfer the PCB. The transfer of the PCB is made by a conveyer belt installed on the conveyer unit. The mounter head installed in the X-Y gantry is used to mount the chips.
FIG. 1 is a perspective view of a conventional surface mounter, FIG. 2 is a perspective view structurely showing a conventional conveyor for supplying PCBs, and FIG. 3 is a plan view of the conveyor of FIG. 2.
Referring to FIGS. 1, 2 and 3, there are shown a frame assembly 100 for supporting a surface mounter, a base assembly 102 disposed on an upper portion of the frame assembly 100 and acting as a base, and a conveyer system 104 installed on an upper portion of the base assembly 102 and for transferring the PCBs.
Further, on an upstream of the conveyer system 104, there is provided an X-Y gantry unit 106 which is operated to move in right, left, forward, and backward directions in order to mount the electronic components, the X-Y gantry unit 106 being comprised of respective gantry frames 109 for supporting an X- and Y-axes.
The gantry frame 109 thus constructed is provided with a movable mounter head assembly 108 used for mounting the components on the PCB transferred by the conveyer system 104.
The mounter head assembly 108 is further provided with a mounter head 120 having a nozzle 112 sucking the components, and a vision unit 114 for carrying out an inspection so that the components sucked can be mounted at the accurate positions on the PCB. Moreover, the conveyer system 104 is provided with a stopper assembly 110 for stopping the transferring of the PCB when the PCB arrives at the work position, a pusher 116 serving to elevate the PCB, and a magnet 118 disposed on a lower portion of the conveyer system 104 to fix the pusher 116.
Further, the conveyer system 104 transferring the PCB is provided with opposing guides 123, 124 disposed parallel to each other on both sides of the base 128, having upper portions thereof on which rails 126 are formed on which both ends of the PCB are placed to be slidably moved thereon. Between both the guides 123, 124, there is installed a push plate 122 having an upper surface on which the stopper assembly 110 is disposed, and in which plural pushers 116 are installed to elevate upward the PCB stopped by said stopper assembly 110 and have respective lower ends thereof to which magnet 118 are installed for fixing the pushers 116 into the push plate 122.
Also, a guide bar 143 is installed in a transversal direction with respect to the guides 123, 124 installed on both sides of the stopper assembly 110.
Further, ball screws 134 are installed on front and rear portions of the guides 123, 134 in a transversal direction with respect thereto, respectively, and has respective one end portion thereof to which driving motors are, respectively, installed. With activation of the driving motor 130, the ball screws 134 are rotated to push the guides 123, 124. Thereby, a smooth supply of the PCBs can be made by an appropriately spread guides in a case of different PCB in size thereof.
However, the conventional PCB transferring apparatus as described above has drawbacks in that when the PCB is suppled to the conveyer unit, the X-Y gantry needs to be moved right and left so that the X-Y gantry is positioned at a designated position for a operation of the picker installed at the mounter head, and the work can be made only by the completion of such an operation, and in that in a case of different dimension of PCB in a lateral and longitudinal sides thereof, an accurate positioning of such a PCB cannot be achieved.
Further, inaccurate positioning of the PCB carried by the conveyer mostly results in an inclination of PCB by a constant angle, and in this case, productivity is lowered and failed products amounts increase due to wreckage and error occurrence of the components, thus resulting in lowered reliability.
To cope with such problems, it may need an extra calibration work, which becomes, however, a significant cause of increased work load.
Therefore, it is an object of the present invention to provide a printed circuit transferring apparatus of a surface mounter, enabling to accurately control the positions where the electronic components are to be mounted on the PCB, to make it possible the work at arbitrary positions, and to further provide an easy compensation for any errors possibly occurring in mounting the electronic components.
The above object is accomplished by the present invention providing a printed circuit transferring apparatus of a surface mounter for mounting various electronic components on a printed circuit board, the apparatus comprising: a frame; an X-Y gantry provided on an upper portion of the frame, the X-Y gantry being moved along the X-Y axes; a base disposed on the frame and placed inside the X-Y gantry; a sensing unit installed on an upper portion of the base, and for sensing the PCB fed from an inlet to determine the position thereof; a PCB transferring unit for freely moving the sensed PCB on the base; and at lease one or more pickup head units installed in the X-Y gantry, and for mounting the electronic components on the PCB having been transferred by the PCB transferring unit.
According to the PCB transferring apparatus thus constructed, it enables to accurately control the positions where the electronic components are to be mounted on the PCB, as well as to make it possible the work at arbitrary positions. Further, as for any errors possibly occurring in mounting the electronic components, easy compensation therefor can be made. Also, with two or more degrees of freedom given to the PCB transferring unit, by which an accurate mounting of the electronic components is made possible, reliability of the products can be further improved.